From: William Lane Craig <info@reasonablefaith.org>Subject: Question of the Week - Atheistic Physicists' Repudiation of Logic and Probability Theory

Date: May 21, 2012 6:40:12 PM GMT+08:00To: lowellgomezperez@aol.com

Reply-To: William Lane Craig <info@reasonablefaith.org>

#266

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Atheistic Physicists' Repudiation of Logic andProbability Theory

Question:

Hello Dr. Craig,

First of all let me say that you are my favorite 'philosopher-missionary' on the scene, and I am justoverjoyed and excited everytime I hear that you went somewhere new in the world! I recently watchedyour debate with the physicist from Finland named Kari . Kari's continued assertion that observations onthe sub-atomic level have shown us that classical logic doesn't model the quantum realm is somethingthat is beginning to appear more and more in the blogosphere. I was hoping to get a deeperexplanation from you about each of the responses you gave in the debate:

1) Quantum logic is held by a tiny minority of physicists.2) You seemed to imply that if we adopt a Bohmeian interpretation of quantum mechanics, then classicallogic applies to the quantum level (does this also imply that quantum logic presupposes theCopenhagen interpretation of quantum mechanics).3) I think you said that classical logic is distinct from the 9 rules of 'formal' logic (i.e. modus ponens,modus tollens, etc.) and your arguments don't rely on things like the law of excluded middle; but canyou really separate these in this manner?4) You also said that your arguments rely on observational evidence at macro-level where classical logicclearly does apply and not on any quantum observations. But didn't the universe began in some sort ofquantum state which might imply that classical logic cannot guide us in our thinking about the origin ofthe universe (i.e. maybe something can come from nothing)?5) It is self-defeating to use formal logic to deny applicability of formal logic at the quantum level.

Thank you,KevinUSA

Dr. Craig responds:

Kevin, I have been scratching my head about this seemingly crazy repudiation of classical logic andprobability theory on the part of certain atheistic physicists ever since my debate with Lawrence Krauss,who took the same line as Kari Enqvist. Krauss even seemed to call into question the truth of theoremsof elementary arithmetic like 2+2=4! What could they be thinking?

Since their repudiation of logic and probability theory was put forward as a response to my theisticarguments, it appeared that they are rejecting the rules of inference of formal sentential logic likemodus ponens, modus tollens, disjunctive syllogism, etc. My conclusions are alleged, it seems, not tofollow because quantum mechanics has overthrown the rules of logic. But that can’t be their contention,for there is nothing in quantum mechanics that would lead one to deny the logical rules of inference,and such a position would be hopeless in any case, since one has then rejected any means of rationallydrawing conclusions—including those of the quantum physicist!

So are they rejecting Aristotelian syllogistic logic? That can’t be right, since my arguments don’t dependupon any peculiarities of Aristotelian logic (like the ability to draw existential conclusions fromuniversally quantified statements) that are not part of modern sentential logic.

So maybe they’re repudiating the classical Law of Excluded Middle, the principle which states that forany proposition p, either p is true or not-p is true. A tiny minority of physicists and philosophers, as Imentioned, have sought to develop a quantum logic according to which, due to indeterminacy, certainstatements about quantum entities or events are neither true nor false. But Enqvist denied that that washis claim, and, as I said, the program of quantum logic wouldn’t affect any of my arguments anyway,since there’s no ground for thinking that the premises of my arguments, which are not about quantumentities or events, are neither true or false.

It sometimes sounded as if Krauss and Enqvist were rejecting the probability calculus. But Bayes’Theorem is a rock-solid formula for how probabilities are to be computed. And in my debate withKrauss I wasn’t even using the Theorem as a whole but just talking about certain factors in it, like theprobability of God’s existence given our background information and certain specific evidence (like thebeginning of the universe, fine-tuning, etc.).

So what in the world are these men talking about?

Well, fortunately, after our debate Enqvist and I went out to lunch together, and I was able to ask himdirectly what he meant. You can imagine my shock when he replied that what he was talking about wasthe violation of the Bell Inequalities by quantum mechanics! My mind shot back to my debate withKrauss, and it suddenly dawned on me that that is what he also must have been talking about! WhenEnqvist said this, I replied that the experimental results on Bell’s Theorem exposed a failure of physicsbut surely not of probability theory itself. But he was adamant, maintaining that the results exposed adeficiency in probability theory, which had predicted the wrong results.

Now this is completely wrong-headed. What John Bell did was use classical probability theory to showthat any physical theory which affirms what is called locality (i.e., there is no action at a distance; alleffects are local) will predict certain statistical results that are at odds with the predictions of quantumtheory. The experimental evidence vindicated the predictions of quantum theory. The evidence thereforestrongly suggests that the physical world is non-local. (Interestingly, the easiest way to have a non-localphysical theory is to abandon Einsteinian special relativity and adopt instead Lorentz’s theory ofrelativity, which permits causal influences to be propagated at super-luminal velocities and thereforehas no problem with the experimental results violating the Bell Inequalities. In fact, Bell’s own personalrecommendation was precisely that we take this Lorentzian route. Bohm’s interpretation of quantummechanics, though fully deterministic, is also a non-local theory featuring absolute simultaneity. For anaccount of the implications of the experimental results on Bell’s Theorem for relativity theory see myTime and the Metaphysics of Relativity, pp. 221-35. But I digress!)

The point is that what the experimental results should lead us to reject is locality, not probability theory!Indeed, if you reject probability theory, then locality and quantum theory are NOT incompatible after all!You could happily embrace both quantum mechanics and local, so-called hidden variable theories byjust blowing off probability theory! So what if the Bell Inequalities are violated by quantum mechanics?Those inequalities were computed using probability theory, so who cares? Ironically, then, theexperimental results to which these physicists appeal to reject probability theory actually presupposeprobability theory!

I hope you can see how perverse this attack on probability theory is. The problem exposed byexperimental science is not probability theory but the assumption of locality. Faulting probability theoryrather than a particular physical theory is like rejecting mathematics because your checkbook fails tobalance—but then Krauss did say 2+2=5, didn’t he?

There are some sobering lessons in all this. First, it shows once again what a gross abuse of sciencesome philosophically naïve physicists are guilty of. (If I have misunderstood these gentlemen, then I ameager to be corrected and to hear an explanation of what they mean.) Second, even to suggest arejection of logic and probability theory in order to avoid theistic conclusions is a sign of desperation.Can you imagine how ridiculed religious people would be if, in order to maintain our view, we had torenounce logic and probability theory? Finally, the tack taken by these thinkers is ultimately counter-productive for them and helpful to theists, for it just is to admit that theism is more logical and moreprobable than atheism.

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